This invention relates to a process of treating oil seed flakes prior to the recovery of oil, wherein the oil seed is comminuted and by means of rolling is formed into flakes having a thickness of about 0.1 to 0.5 mm, before they are supplied to the recovery of oil.
Processes of this type are known and described for instance in DE-A-24 07 453. There is performed a moisture-heat treatment of the oil seeds in a multi-stage shaking trough. When refining the oils recovered there is the difficulty that degumming only by means of a water treatment leaves too much phosphatides in the oil, so that this oil cannot be refined physically with an economically acceptable effort.
It is the object underlying the invention to deactivate disturbing amounts of enzymes in the oil seed, in order to eliminate the formation of non-hydratable phosphatides during the recovery of oil in the oil press and/or extraction, which phosphatides would otherwise get into the oil recovered and render degumming and refining more difficult. In accordance with the invention this is achieved in that the flakes are charged into a transporting mixer with a temperature of 20 to 50xc2x0 C., to which mixer steam and/or water are supplied at the same time, that the flakes in the mixer are transported to the outlet of the mixer with a dwell time of 5 to 50 seconds, and at the outlet flakes are withdrawn from the mixer with temperatures in the range from 90 to 110xc2x0 C. and a moisture content of 8 to 20 wt-%, that the flakes from the mixer are passed through an annealing zone in which the flakes are moved over heated trays with dwell times of 15 to 50 minutes and temperatures in the range from 90 to 110xc2x0 C., that the flakes are withdrawn from the annealing zone with a residual moisture which still amounts to at least half the moisture content at the inlet of the annealing zone, and that the flakes are passed through a drying zone with temperatures of 90 to 120xc2x0 C. and a cooling zone, until oil seed granules are formed, before the granules are charged into a press and/or extraction for the recovery of oil.
The process is chiefly suited for rape seed, but also for sunflower seed, soybeans and linseed. Due to the heat treatment with simultaneous presence of moisture in the transporting mixer and in the annealing zone the deactivation of enzymes is achieved, which would render the refining of oil more difficult. These enzymes include in particular phospholipase and lipoxygenase and in the case of rape seed especially also myrosinase. By means of the deactivation, the increase of non-hydratable phosphatides in the crude oil during the recovery in the oil press and also in a solvent extraction is wholly or largely prevented. As a result, the phosphatide content in the crude oil recovered can be reduced by means of a simple water treatment for degumming such that the oil degummed can directly be supplied to the physical refining. In degumming by means of water, the hydratable phosphatides (lecithin) are separated. Non-hydratable phosphatides (NHP) are, however, left in the crude oil which is supplied to refining. The relatively simple physical refining (bleaching and deodorizing) is sufficient in the present case, as water degumming of the crude oil recovered from rape seed, sunflower seed or soybeans already lowers the phosphatide content sufficiently.
In the recovery of oil from rape seed, an important product not only is the oil, but also the rape grit which is used as feedstuff. When the activity of myrosinase in the rape flakes is too high, the further treatment of the solids (expellers) from the oil press also leads to a rape grit which contains disturbing amounts of decomposition products, which are caused by the activity of myrosinase. By deactivating the disturbing enzymes already before the oil press it is now advantageously achieved that the disturbing enzymes and also the myrosinase are biochemically inactivated, which facilitates degumming and keeps away disturbing amounts of decomposition products from the rape grit.
Advantageously, the oil seed flakes are charged into the transporting mixer with a moisture content of 3 to 12 wt-%, to which mixer additional moisture is supplied. Expediently, the flakes are heated in the transporting mixer to a temperature of 80xc2x0 C. within 3 to 10 seconds. It was noted that up to a temperature in the range from about 70 to 75xc2x0 C. enzymatic reactions take place in the flakes to an increased extent, which reactions lead to undesired substances. By means of a rapid heating in the transporting mixer the formation of these disturbing substances can be prevented or be maintained at a low level.
The process is particularly suited for processing rape seed, because in addition to the above-mentioned lipases, there can also largely be deactivated the enzyme myrosinase, which is typical for rape seed. During the recovery of oil from rape species with a higher or high content of thioglucosides (GLS), non-deactivated myrosinase leads to undesired decomposition processes (hydrolysis) of GLS, where volatile isothiocyanates (ITC) and non-volatile oxazolidine thiones (VOT) are obtained as reaction products, which can impair the oil cake, the rape grit and the oil quality. Due to the product structure of the rape granules there is furthermore provided the possibility to perform a direct extraction of the rape flakes with economically acceptable means without use of an oil press.